Internal jugular vein collapsibility index versus common carotid artery peak systolic velocity variation for prediction of post-spinal hypotension: A prospective observational study

Abstract

Background and Aims:

Post-spinal anesthesia hypotension (PSAH) is associated with significant adverse outcomes, prompting extensive research into predictive markers. This study aimed to evaluate and compare the predictive value of the internal jugular vein collapsibility index (IJV-CI) and common carotid artery peak systolic velocity variation (CCA-PSV) in forecasting PSAH.

Material and Methods:

A prospective observational study was conducted on 53 ASA I, II, and III adult patients undergoing elective surgery under spinal anesthesia (SAB). IJV-CI and CCA-PSV were examined using ultrasonography in all patients. SAB was administered using a standard protocol. PSAH was defined as a reduction of systolic blood pressure (SBP) ≥20%. Our primary objective was to evaluate the predictive value of IJV-CI and CCA-PSV for PSAH. The secondary objective was to compare their diagnostic efficacy.

Results:

PSAH was found in 39.6% (21 out of 53) patients. The area under the ROC curve for IJV-CI was 0.769 (95% CI: 0.903–0.636, P = 0.001). IJV-CI > 21.58% predicted PSAH with 71.43% sensitivity, 84.38% specificity, and 79.25% accuracy. The area under the ROC curve for CCA-PSV was 0.760 (95% CI: 0.888–0.631, P = 0.002). CCA-PSV >12.16% predicted PSAH with 85.71% sensitivity, 56.25% specificity, and 67.92% accuracy. With the maximum % fall in SBP, IJV-CI had a significantly low-positive correlation (r = 0.298, P = 0.030), and CCA-PSV had a significant moderate positive correlation (r = 0.483, P = 0.0002).

Conclusions:

Both IJV-CI and CCA-PSV are reliable predictors of PSAH. In terms of accuracy, IJV-CI is a better predictor of hypotension post-spinal anesthesia as compared to CCA-PSV.

Introduction

Post-spinal anesthesia hypotension (PSAH) is one of the frequently encountered complications, with its incidence ranging between 30% and 40%.[1] Occurring as a consequence of sympatholysis following spinal anesthesia, it can subsequently lead to tissue underperfusion, ischemia of the vital organs, poor postoperative outcome, prolonged hospital stay, and an increase in morbidity and mortality.[2,3,4] The early prediction of post-spinal hypotension is important for a successful outcome, as timely interventions may prevent any untoward event.

Ultrasonography, a non-invasive, readily available, and real-time tool, is rapidly replacing traditional invasive methods for hemodynamic monitoring. Sonographically assessed parameters that are simple and less time-consuming like internal jugular vein collapsibility index (IJV-CI) and common carotid artery peak systolic velocity variation (CCA-PSV) have gained popularity for assessing the volume status and fluid responsiveness in different patient populations, especially mechanically ventilated and critically ill patients.[5,6,7,8,9,10,11]

Recently, they have been individually investigated as predictors of hypotension following spinal and general anesthesia. IJV area (IJV-A) and IJV-CI assessed in the Trendelenburg position prior to the initiation of general anesthesia were shown to be helpful in the prediction of hypotension during induction.[5,6] Investigators found the IJV collapsibility index to be a reliable indicator to predict hypotension in adult, pregnant, and elderly patients undergoing spinal anesthesia.[7,8,9] Studies exploring the role of CCA-PSV in the prediction of PSH are scarce, thus yielding insufficient evidence.[10,11]

To date, no research has compared the IJV collapsibility index and CCA peak systolic variation in the prediction of PSAH. Hence, we compared the diagnostic efficacy of both parameters in predicting hypotension after spinal anesthesia.

Material and Methods

This prospective, observational study was registered in the Clinical Trials Registry-India (CTRI/2023/03/051126, http;//ctri.nic.in/) after approval by the Institutional Ethics Committee (vide approval number BFUHS/2k23p-TH/13149). A total of 53 adult American Society of Anesthesiologists physical status classification I, II, and III patients undergoing surgery under spinal anesthesia were recruited for the study. Patients with any contraindication to spinal anesthesia, refusal to participate in the study, presence of any wound/dressing/swelling/structural abnormality in the neck, pregnancy or pre-existing severe cardiac, renal, or liver disease were excluded from the study. Informed written consent was obtained after explaining the study protocol. The procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation and with the Helsinki Declaration of 1975, as revised in 2000. The reporting of this study conformed to the Standards for Reporting of Diagnostic Accuracy Studies.

After shifting the patient to the operating room, the patient was positioned in the supine position, and standard monitoring was started using non-invasive blood pressure (NIBP), pulse oximetry, and five-lead electrocardiography. The baseline values of NIBP, oxygen saturation, and pulse rate were recorded after taking a mean of two successive readings 2 minutes apart. Patients were then subjected to an ultrasound examination of the neck.

For IJV collapsibility index measurement, the neck of the patient was turned to the left side, and the head end was elevated to 30°. A high-frequency (6–13 MHz) linear ultrasound (FUJIFILM SONOSITE EDGE II) probe was then placed horizontally to the right-hand side of the middle of the thyroid cartilage. A clear, circular cross-sectional image of the right IJV was obtained by rotating the probe clockwise or counterclockwise with minimal pressure on the IJV. Using M-mode, maximum (IJV max) and minimum (IJV min) antero-posterior diameters of IJV were measured [Figure 1a]. The IJV collapsibility index was derived by the formula: IJV-CI = (IJV max − IJV min)/IJV max × 100.

Figure 1.

(a): Ultrasound image of right IJV in M-mode, where A, B: Maximum diameter C, D: Minimum diameter and (b): Ultrasound image of right CCA in wave Doppler B-mode, where A, B: Maximum peak systolic velocity C, D: Minimum peak systolic velocity. CCA: Common carotid artery; IJV: Internal jugular vein

For CCA-PSV measurements, the patient was kept in the supine position with the neck turned to the left side. Using the same ultrasound probe, the right carotid artery measurements were obtained at 2 cm proximal from the carotid artery bifurcation. In the long-axis view, B-mode wave Doppler was used to obtain waveforms of CCA at a 60° insonation angle. The maximum peak systolic velocity (PSV max) and minimum peak systolic velocity (PSV min) were measured from the spectral Doppler tracing with a sweep speed of 50 mm/s [Figure 1b]. Two readings of PSV max and PSV min were recorded, and their mean was calculated. Common carotid artery peak systolic velocity variation was calculated as follows: CCA-PSV = (PSV max − PSV min/PSV mean) ×100

where PSV mean = (PSV max + PSV min)/2

Two readings of IJV-CI and CCA-PSV were obtained, and their mean values were calculated and recorded. All sonographic measurements were evaluated by a single senior anesthesiologist with experience in critical care ultrasonography for more than 3 years.

While preparing the patient for spinal anesthesia, co-loading with crystalloid solution (10 mL/kg) was initiated. Subarachnoid block was performed using a 26 G Quincke needle in L₃–L₄ interspace, and 12.5 mg bupivacaine heavy 0.5% (2.5 mL) with 25 μg fentanyl (0.5 mL) was injected in the subarachnoid space in the sitting position.

Patient’s heart rate (HR), NIBP, and oxygen saturation (SpO₂) were monitored and recorded immediately post-spinal anesthesia (zero minutes) and then after every 2 minutes for the first 30 minutes, as per standard protocol by the attending anaesthesiologist. The level of sensory block was assessed by loss of pinprick sensation, and the level of the motor block was evaluated using the Modified Bromage Scale every 5 minutes till 30 minutes. The highest level/degree of sensory and motor block achieved was recorded.

Surgical procedure was permitted when the required level of sensory and motor blockade was attained. PSAH was defined as a reduction of the systolic blood pressure (SBP) of more than or equal to 20% of the baseline value after spinal anesthesia.[12] The PSAH was treated with rapid IV fluid administration and intermittent boluses of ephedrine 6 mg as needed. Bradycardia was described as a HR going below 60 beats per minute and was managed with IV administration of 0.6 mg of atropine. Oxygen supplementation was given when the saturation fell below <94% or the patient developed significant bradycardia or hypotension.

Our primary objective was to evaluate the predictive value of IJV-CI and CCA-PSV for post-spinal hypotension. Our secondary objective was to compare their diagnostic efficacy.

Statistical analysis

All statistical calculations were performed using the Statistical Package for the Social Sciences 21.0 version (SPSS Inc., Chicago, IL, USA) statistical program for Microsoft Windows. The continuous variables were presented in terms of mean ± standard deviation (± SD) and categorical variables in terms of frequencies (number of cases) and relative frequencies (percentages) as appropriate. The Kolmogorov-Smirnov test was used to determine whether the normally distributed data. Comparison of quantitative variables between the study groups, like age, height, weight, BMI, carotid peak velocity, carotid artery peak velocity variation, IJV diameter, and IJV collapsibility index, was performed using the Z test. A Chi-square (χ2) test was performed to compare categorical data.

Measures of diagnostic efficacy, such as sensitivity, specificity, and positive and negative predictive values, along with positive and negative likelihood ratios, were calculated to determine the diagnostic accuracy of IJV-CI and CCA-PSV in predicting PSAH. The receiver operator characteristics (ROC) curve was then obtained to derive the cut-off value of IJV-CI and CCA-PSV, and the area under the ROC curve (AUROC) was measured. Spearman’s rho correlation was used to test for the linear relation of maximum % fall in SBP with IJV-CI and CCA-PSV. A probability value (P) less than 0.05 was considered statistically significant.

Sample size calculation for this study was performed by the following formula:

Sample size based on sensitivity = Z²* S_N * (1-S_N)/L*p

Sample size based on specificity = Z²* S_P * (1-S_P)/L²* (1-p)

Where S_N – Sensitivity

S_P – Specificity

p – Prevalence of hypotension

L – Absolute precision desired on either side of sensitivity and specificity

Z – Standard normal deviate corresponding to the specified size of the critical region

The sample size of 48 was estimated considering the sensitivity of 64% and specificity of 63.6% of the IJV collapsibility index in predicting PSH as found in a previous study by Kılıç Y.[7]

The sample size of 47 was estimated considering the sensitivity of 70.6% and specificity of 54.6% of CCA peak flow velocity variation in predicting PSH as found in a previous study by Chowdhary S.[10]

Therefore, for our study, considering the power analysis to achieve a power of 80%, the highest value, which was 48 cases, was taken. Hence, the total sample size taken was 53, considering 10% dropout.

Results

A total of 55 patients were assessed for eligibility, recruited, and administered spinal anesthesia. Two patients had failed effect of spinal anesthesia and were not analyzed. Out of the 53 patients analyzed, PSAH occurred in 21 patients [39.6%], and no patient had bradycardia after spinal anesthesia. Patients were divided into two groups: with PSAH and without PSAH. Though demographic characteristics were similar in both groups, hemodynamic parameters, baseline HR, baseline SBP, and maximum % fall in SBP post-spinal anesthesia, were significantly higher in patients with PSAH [Table 1].

Table 1.

Demographic and hemodynamic characteristics of all patients

Parameter	All patients	Patients with PSAH	Patients without PSAH	P
Age (years)	43.57±14.78	44.05±17.07	43.25±13.34	0.85*
Gender (male/female); n (%)	41 (77.4)/12 (22.6)	15 (71.42)/6 (28.57)	26 (81.25)/6 (18.75)	0.403†
Weight (kg)	76.02±17.88	78.52±21.86	74.38±14.87	0.414*
Height (cm)	169.64±8.21	169.52±8.48	169.72±8.16	0.934*
BMI (kg/m2)	26.28±4.63	26.94±5.59	25.69±3.90	0.341*
ASA I/II/III	21/26/6	7/13/1	14/13/5	0.242†
Baseline SBP (mmHg)	140.23±16.71	146.90±18.11	135.84±14.38	0.027*
Baseline HR (bpm)	87.17±14.42	92.67±16.64	83.56±11.68	0.048*
Maximum fall in SBP (%)	20.47±8.22	29.24±5.12	14.71±3.17	0.001*

Values are presented as mean±SD or frequency (%). PSAH: post-spinal anesthesia hypotension, n: frequency, BMI: body mass index, ASA: American Society of Anaesthesiologists physical status classification, SBP: systolic blood pressure, HR: heart rate; Tests of significance: *Z test, ^†Chi-square test

Ultrasonographic parameters measured are shown in Table 2. The IJV-CI was significantly higher in patients with PSAH (P = 0.001). The minimum carotid peak velocity was significantly lower (P = 0.038), and CCA-PSV was significantly higher (P = 0.003) in patients with PSAH.

Table 2.

Ultrasonographic parameters of all patients

Parameter	All patients	Patients with PSAH	Patients without PSAH	P	95% confidence interval
IJV max (cm)	0.92±0.31	0.84±0.27	0.97±0.33	0.182	−0.05–0.29
IJV min (cm)	0.75±0.29	0.64±0.24	0.82±0.31	0.054	0.02–0.34
IJV-CI (%)	19.59±9.02	24.84±9.71	16.14±6.68	0.001	−13.22–−4.19
PSV max (cm/s)	18.37±5.15	17.06±4.23	19.23±5.56	0.229	−0.69–5.04
PSV min (cm/s)	15.94±4.80	14.27±3.82	17.04±5.11	0.229	0.15–5.39
PSV mean (cm/s)	17.17±4.93	15.66±3.99	18.17±5.28	0.096	−0.21–5.23
CCA-PSV (%)	14.54±6.91	18.24±7.58	12.11±5.25	0.003	−9.67–−2.60

Values are presented as mean±SD. PSAH: post-spinal anesthesia hypotension, IJV: Internal jugular vein, IJV-CI: Internal jugular vein collapsibility index, PSV: peak systolic velocity, CCA-PSV: Common carotid artery peak systolic velocity variation; statistical test used: Z test

The AUROC for IJV-CI for predicting PSAH was 0.769 (95% CI = 0.903–0.636, P = 0.001). IJV-CI >21.58% predicted PSAH with sensitivity and specificity of 71.43% and 84.38%, respectively, 81.82% negative predictive value (NPV), and 79.25% accuracy (P = 0.001) [Table 3, Figure 2]. The AUROC for CCA-PSV was 0.760 (95% CI = 0.888–0.631, P = 0.002). CCA-PSV >12.16% predicted PSH with sensitivity and specificity of 85.71% and 56.25%, respectively, 85.71% NPV, and 67.92% accuracy (P = 0.004) [Table 3, Figure 3].

Table 3.

Diagnostic profile of IJV-CI and CCA-PSV in the prediction of PSAH

	IJV-CI	CCA-PSV
Cut-off value	21.58%	12.16%
AUC	0.769	0.760
95% confidence interval	0.639–0.903	0.631–0.888
P	0.001*	0.002*
Sensitivity (%)	71.43	85.71
Specificity (%)	84.38	56.25
PPV (%)	75.00	56.25
NPV (%)	81.82	85.71
Accuracy (%)	79.25	67.92

IJV-CI: Internal jugular vein collapsibility index, CCA-PSV: Common carotid artery peak systolic velocity variation, AUC: area under curve, PPV: positive predictive value, NPV: negative predictive value. *Statistically significant as P<0.05

Figure 2.

Receiver operating characteristic curve of IJV collapsibility index in prediction of PSAH. IJV: Internal jugular vein; PSAH: Post-spinal anesthesia hypotension

Figure 3.

Receiver operating characteristic curve of carotid artery peak systolic velocity variation in the prediction of PSAH. PSAH: Post-spinal anesthesia hypotension

On comparing IJV-CI with maximum % fall in SBP, a statistically significant low-positive correlation was present (r = 0.298, P = 0.030). A statistically significant moderate positive correlation (r = 0.483, P = 0.0002) was present between CCA-PSV and maximum % fall in SBP.

Discussion

In our study, we compared the diagnostic efficacy of the IJV collapsibility index with CCA-PSV variation in the prediction of hypotension post-spinal anesthesia in the same patient. Demographic parameters such as age, gender, and BMI may act as confounding factors for the development of post-spinal hypotension, but in our study, there was no statistically significant difference in these parameters among patients, with and without the development of PSAH. In our study, 39.6% (21 out of 53) patients had PSAH, and this finding is in concordance with the study conducted by Jeon et al.[13] and Chowdhury et al.[10] where the incidence of hypotension was 41% and 34%, respectively. On the contrary, the incidence of hypotension reported in the geriatric and obstetric populations was remarkably higher (47% and 66.2%, respectively).[8,9]

We assessed the IJV diameter ultrasonographically, and IJV-CI was derived from it. Patients with PSAH (24.84%) had significantly higher mean IJV-CI value than patients without PSAH (16.14%) (P = 0.001). The cut-off value of IJV-CI calculated was 21.58% with sensitivity and specificity of 71.43% and 84.38% respectively, with 79.25% accuracy for predicting PSAH. The AUROC was 0.769 with a cut-off value of 21.58% (95% CI 0.903-0.636, P = 0.001).

Kılıç et al.[7] also observed IJV-CI to be a moderate predictor of PSAH with cut-off value of 22.6%. They reported an AUROC of 0.709, sensitivity of 64%, and specificity of 63.6% with P = 0.014.

The cut-off value of IJV-CI for the prediction of PSAH found by Abdelhamid et al.[8] in geriatric patients was >34.4% with a sensitivity of 61.70% and a specificity of 79.17% with an AUROC of 0.69 (95% CI: 0.578–0.802).

IJV-CI was also used for the prediction of hypotension post-induction in general anesthesia by Kılıç et al.[6] With an AUROC of 0.704, the IJV collapsibility index in the Trendelenburg position had a cut-off point of 19.9% with 62% sensitivity and 62% specificity to predict the episode of hypotension post-induction of anesthesia and was considered a reliable indicator.

IJV-CI was found to be a reliable, easy-to-acquire, non-invasive measure of fluid responsiveness and appeared to be a suitable supplement to IVC-CI. IJV-CI greater than 36% predicted hypovolemia and fluid responsiveness in sepsis, with a sensitivity and specificity of 78% and 85%, respectively, in patients admitted to the intensive care unit.[14] In another study for bedside assessment of central venous pressure and fluid status in critically ill patients, the IJV-CI had a cut-off >21.4% with a sensitivity of 88.4%, specificity of 79.2%, and accuracy of 85.1% for predicting CVP ≤10.[15]

When used to predict hypotension post-spinal anesthesia in pregnant females, higher IJV-CI cut-off values of 38.5% with sensitivity and specificity of 84.6 and 82.8%, respectively, in contrast to our study.[9] The exclusion of pregnant females in our patient selection might have led to a lower cut-off value. On the other hand, recent research conducted by authors Pharanitharan et al.[16] and Derya et al.[17] have determined that IJV-CI was not an adequate predictor of post-spinal hypotension. Hence, it is debatable whether IJV-CI is a reliable indicator of post-spinal hypotension. Therefore, we conducted an ultrasonographic analysis of the carotid artery to predict hypotension.

Recent studies have shown carotid artery parameters like carotid cross-sectional area, PSV variation to be reliable and accurate when determining the patient’s volume status.[18,19,20] We evaluated CCA-PSV, which describes how changes in respiratory fluctuations cause the carotid pulse upstroke’s amplitude to change. We analyzed CCA-PSV. Using ultrasonographic wave Doppler, maximum and minimum carotid artery peak systolic velocities were measured in one respiratory cycle. Carotid artery PSV variation was derived from the carotid velocities. It was found that the mean CCA-PSV was 18.24% in patients who had hypotension and 12.11% in patients who had no hypotension. The patients who developed hypotension expressed significantly higher CCA-PSV values than patients who did not develop hypotension (P = 0.003).

With an AUROC of 0.760 (95% CI: 0.888–0.631, P = 0.004) for CCA-PSV, the sensitivity and specificity were 85.71% and 56.25%, respectively, with 67.92% accuracy for predicting PSAH. In a research on predicting fluid responsiveness in mechanically ventilated patients, a similar cut-off value of CCA-PSV 11% was found with a sensitivity of 85% and specificity of 82% and an AUROC of 0.85 with a 95% CI of 0.72–0.97 and a significant P = 0.001.[18]

In contrast to our results, Maitra et al.[11] reported optimum cut-off value of CCA-PSV for prediction of hypotension to be 18.8% with sensitivity (61.9%) and specificity (67.4%) lower than our study, with an AUROC curve of 0.68 with 95% CI 0.58–0.78. The factors that made CCA-PSV not a reliable predictor in their study could be the inclusion of ASA I, ASA II patients, not the elderly or sick patients for whom the risk of hypotension increases.

Chowdhury et al.[10] also reported the cut-off value of 18.33% which was higher in comparison with our study (12.16%). The sensitivity (70.6%) was lower, whereas the specificity (54.6%) reported was similar to our study, with an area under the ROC of 0.639.

In our study, Spearman’s rho correlation coefficient was used to find out the correlation between the parameters of CCA-PSV, IJV-CI, and maximum fall in SBP. It was observed that the association of IJV-CI and post-spinal maximum fall in SBP had a positive correlation (r = 0.298) that was statistically significant P = 0.030. This indicates that the higher the IJV-CI value, more are the chances of hypotension.

CCA-PSV had a moderate positive correlation (r = 0.483) with maximum percent fall in SBP. This finding was statistically significant, P = 0.0002. This infers that the higher the CCA-PSV, the greater will be the maximum percent fall in SBP.

On comparison between two parameters, a similar AUROC of 0.769 and 0.760 for IJV-CI and CCA-PSV, respectively, was observed. The IJV-CI had a better specificity of 84.38%, and the CCA-PSV had a better sensitivity of 85.71%. Accuracy, as defined in literature, refers to the closeness of a measurement to the true value of the quantity being measured was better with IJV-CI (79.25%) than CCA-PSV (67.92%) in our study for the prediction of post-spinal hypotension.

One of the key strengths of our study is the elimination of inter-evaluator variability, as a single evaluator performed all measurements. Additionally, both parameters were assessed in the same patient, minimizing patient-related bias. To our knowledge, this is the first study to compare the diagnostic efficacy of ultrasonographic internal jugular vein measurements with ultrasonographic carotid artery measurements for predicting post-spinal hypotension.

However, our study has certain limitations. It is a single-center observational study with a relatively small sample size, limited to elective surgical patients.

Conclusion

Both IJV-CI and CCA-PSV are significantly useful for the prediction of post-spinal hypotension, with IJV-CI being more specific (84.38%) and CCA-PSV being a more sensitive (85.71%) indicator. In terms of accuracy, IJV-CI is a better and more accurate predictor of PSAH as compared to CCA-PSV.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.